The reactivity of both coupling partners—the glycosyl donor and acceptor—is decisive for the outcome of a glycosylation reaction, in terms of both yield and stereoselectivity. Where the reactivity of glycosyl donors is well understood and can be controlled through manipulation of the functional/protecting‐group pattern, the reactivity of glycosyl acceptor alcohols is poorly understood. We here present an operationally simple system to gauge glycosyl acceptor reactivity, which employs two conformationally locked donors with stereoselectivity that critically depends on the reactivity of the nucleophile. A wide array of acceptors was screened and their structure–reactivity/stereoselectivity relationships established. By systematically varying the protecting groups, the reactivity of glycosyl acceptors can be adjusted to attain stereoselective cis‐glucosylations.

The reactivity of both coupling partners-the glycosyl donor and acceptor-is decisive for the outcome of ag lycosylation reaction, in terms of both yield and stereoselectivity.W here the reactivity of glycosyl donors is well understood and can be controlled through manipulation of the functional/protecting-group pattern, the reactivity of glycosyl acceptor alcohols is poorly understood. We here present an operationally simple system to gauge glycosyl acceptor reactivity,which employs two conformationally locked donors with stereoselectivity that critically depends on the reactivity of the nucleophile.Awide arrayo fa cceptors was screened and their structure-reactivity/stereoselectivity relationships established. By systematically varying the protecting groups,t he reactivity of glycosyl acceptors can be adjusted to attain stereoselective cis-glucosylations. Scheme 1. General glycosylation mechanism, showing the equilibrium of reactive species. Pg = protecting group. Figure 1. Donors A and B and C-4-OH glucosyl acceptors 1-20.

The stereoselectivity of glycosylation … … reactions can depend critically on the reactivity of the acceptor glycoside (the nucleophile in the reaction). In their Communication on page 8240 ff., J. D. Codée et al. report a facile system that maps the relationship between glycosyl acceptor reactivity and glycosylation stereoselectivity. Tuning the reactivity of the nucleophile through the judicious choice of protecting groups can provide stereoselective 1,2‐cis‐glycosylations.

Die Stereoselektivität von Glykosylierungen kann ganz zentral von der Reaktivität des Akzeptor‐Glykosids (des Nukleophils in der Reaktion) abhängen. J. D. Codée et al. berichten in ihrer Zuschrift auf S. 8372 ff. über ein einfaches System, um die Beziehung zwischen der Reaktivität des Glykosyl‐Akzeptors und der Stereoselektivität der Glykosylierung zu kartieren. Die Feinabstimmung der Reaktivität des Nukleophils durch sorgfältige Wahl der Schutzgruppen ermöglicht stereoselektive 1,2‐cis‐Glykosylierungen.